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authorDavid Brownell <dbrownell@users.sourceforge.net>2008-11-06 15:53:40 -0500
committerLinus Torvalds <torvalds@linux-foundation.org>2008-11-06 18:41:19 -0500
commit06a7f058761cd232cab42d5c7da82f7255b51d5b (patch)
tree252628da8a885a2f2c0ca6488e110a7e1fb2d169 /drivers/serial
parentb225d44e27521290faca2e0f9b1a4a8c74dc510a (diff)
atmel_serial: keep clock off when it's not needed
The atmel_serial driver is mismanaging its clock by leaving it on at all times ... the whole point of clock management is to leave it off unless it's actively needed, which conserves power!! Although the kernel doesn't actually hang without my fix, it does discard quite a lot of early console output. The result still looks correct: usart users= 1 on 35000000 Hz, for atmel_usart.0 usart users= 0 off 35000000 Hz, for atmel_usart.2 when using ttyS0 as serial console. [haavard.skinnemoen@atmel.com: Make sure clock is enabled early for console] Signed-off-by: David Brownell <dbrownell@users.sourceforge.net> Signed-off-by: Haavard Skinnemoen <haavard.skinnemoen@atmel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'drivers/serial')
-rw-r--r--drivers/serial/atmel_serial.c17
1 files changed, 14 insertions, 3 deletions
diff --git a/drivers/serial/atmel_serial.c b/drivers/serial/atmel_serial.c
index 61fb8b6d19af..d5efd6c77904 100644
--- a/drivers/serial/atmel_serial.c
+++ b/drivers/serial/atmel_serial.c
@@ -1258,6 +1258,8 @@ static void __devinit atmel_init_port(struct atmel_uart_port *atmel_port,
1258 atmel_port->clk = clk_get(&pdev->dev, "usart"); 1258 atmel_port->clk = clk_get(&pdev->dev, "usart");
1259 clk_enable(atmel_port->clk); 1259 clk_enable(atmel_port->clk);
1260 port->uartclk = clk_get_rate(atmel_port->clk); 1260 port->uartclk = clk_get_rate(atmel_port->clk);
1261 clk_disable(atmel_port->clk);
1262 /* only enable clock when USART is in use */
1261 } 1263 }
1262 1264
1263 atmel_port->use_dma_rx = data->use_dma_rx; 1265 atmel_port->use_dma_rx = data->use_dma_rx;
@@ -1379,6 +1381,8 @@ static int __init atmel_console_setup(struct console *co, char *options)
1379 return -ENODEV; 1381 return -ENODEV;
1380 } 1382 }
1381 1383
1384 clk_enable(atmel_ports[co->index].clk);
1385
1382 UART_PUT_IDR(port, -1); 1386 UART_PUT_IDR(port, -1);
1383 UART_PUT_CR(port, ATMEL_US_RSTSTA | ATMEL_US_RSTRX); 1387 UART_PUT_CR(port, ATMEL_US_RSTSTA | ATMEL_US_RSTRX);
1384 UART_PUT_CR(port, ATMEL_US_TXEN | ATMEL_US_RXEN); 1388 UART_PUT_CR(port, ATMEL_US_TXEN | ATMEL_US_RXEN);
@@ -1403,7 +1407,7 @@ static struct console atmel_console = {
1403 .data = &atmel_uart, 1407 .data = &atmel_uart,
1404}; 1408};
1405 1409
1406#define ATMEL_CONSOLE_DEVICE &atmel_console 1410#define ATMEL_CONSOLE_DEVICE (&atmel_console)
1407 1411
1408/* 1412/*
1409 * Early console initialization (before VM subsystem initialized). 1413 * Early console initialization (before VM subsystem initialized).
@@ -1534,6 +1538,15 @@ static int __devinit atmel_serial_probe(struct platform_device *pdev)
1534 if (ret) 1538 if (ret)
1535 goto err_add_port; 1539 goto err_add_port;
1536 1540
1541 if (atmel_is_console_port(&port->uart)
1542 && ATMEL_CONSOLE_DEVICE->flags & CON_ENABLED) {
1543 /*
1544 * The serial core enabled the clock for us, so undo
1545 * the clk_enable() in atmel_console_setup()
1546 */
1547 clk_disable(port->clk);
1548 }
1549
1537 device_init_wakeup(&pdev->dev, 1); 1550 device_init_wakeup(&pdev->dev, 1);
1538 platform_set_drvdata(pdev, port); 1551 platform_set_drvdata(pdev, port);
1539 1552
@@ -1544,7 +1557,6 @@ err_add_port:
1544 port->rx_ring.buf = NULL; 1557 port->rx_ring.buf = NULL;
1545err_alloc_ring: 1558err_alloc_ring:
1546 if (!atmel_is_console_port(&port->uart)) { 1559 if (!atmel_is_console_port(&port->uart)) {
1547 clk_disable(port->clk);
1548 clk_put(port->clk); 1560 clk_put(port->clk);
1549 port->clk = NULL; 1561 port->clk = NULL;
1550 } 1562 }
@@ -1568,7 +1580,6 @@ static int __devexit atmel_serial_remove(struct platform_device *pdev)
1568 1580
1569 /* "port" is allocated statically, so we shouldn't free it */ 1581 /* "port" is allocated statically, so we shouldn't free it */
1570 1582
1571 clk_disable(atmel_port->clk);
1572 clk_put(atmel_port->clk); 1583 clk_put(atmel_port->clk);
1573 1584
1574 return ret; 1585 return ret;